FIG. 1 is a structure diagram of a digital communication system. As shown in FIG. 1, the digital communication system may include a transmitting terminal and a receiving terminal, and the transmitting terminal and the receiving terminal may communicate with each other through a channel. Generally, the transmitting terminal may mainly include: an information source, an information source encoder, a channel encoder and a modulator. The receiving terminal may mainly include: a demodulator, a channel decoder, an information source decoder and an information sink. The main function of the encoder is: introducing redundant information in an information bit according to certain rules, so that the channel decoder of the receiving terminal may correct, to some extent, error codes generating when information is transmitted in a channel.
Baseband processing plays an important role in wireless interface technologies. The baseband processing before physical channel mapping is mainly the processing of channel encoding chain in the channel encoder. FIG. 2 is a flowchart of processing of channel encoding chain. As shown in FIG. 2, the processing of channel encoding chain is: performing code block division to an input Transport Block (TB), namely dividing the TB entering the channel encoder into code blocks according to the size of the maximum code block. The TB is a basic input of the channel encoding chain. Generally, data of one TB may be processed by the same encoding and modulating mode. Operations like Cyclic Redundancy Check (CRC) adding, channel encoding, rate matching, modulation, and physical channel mapping may be performed on multiple obtained code blocks.
FIG. 3 is a schematic diagram of code block division. As shown in FIG. 3, in an encoding process of a channel encoder, the channel encoder may divide the information bit of the TB into the encoding bocks with a certain length. In FIG. 3, for example, the TB may be divided into the code block 1, the code block 2 and the code block 3. Generally, the bigger the code block, the better the error-correcting performance. But if the code block is big, encoding and decoding complexity and decoding delay time may increase. Therefore, when a channel encoder is designed, it may be suggested to limit the size of the maximum code block, that is, a maximum value of a maximum code block may be set. Because an allowable size of the maximum code block may be provided for the channel encoding, it may be needed to divide one TB into multiple code blocks before channel encoding can be performed. At present, in the process of dividing the TB into multiple code blocks (namely a code block division technology), it may be needed to divide a TB into multiple code blocks with roughly the same size. For example, in a 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) and LET-Advanced (LTE-A) system, the code block division may be performed by taking 6144 bits as a unit. When the length of the TB (including the CRC) is greater than 6144 bits, one TB may be divided into multiple code blocks. Moreover, because the length of the code block and the length of the CRC is required to match a code length supported by a turbo channel encoder, and the code blocks not matching the code length supported by the channel encoder cannot be directly encoded, so it may also be needed to add filling bits to these code blocks.
The LTE and LTE-A system is a system based on Orthogonal Frequency Division Multiplexing (OFDM). In an OFDM system, a physical time frequency Resource Block (RB), which may be called RB for short, is a time frequency two-dimensional unit composed of multiple OFDM symbols which are continuous on time and multiple subcarriers which are continuous on frequency. FIG. 4 is a schematic diagram of an RB whose time length is one time slot in the OFDM system. As shown in FIG. 4, an RB may occupy 12 subcarriers in a frequency domain. In the LTE and LTE-A system, a basic time granularity of resource allocation is an integral multiple of one subframe, and a frequency domain granularity is an integral multiple of one RB (namely 12 subcarriers). In an RB structure in FIG. 4, one time slot may include 7 continuous OFDM symbols, and one subcarrier may include two time slots, namely 14 continuous OFDM symbols. In addition, each small square in FIG. 4 represents one Resource Element (RE). In one time slot, there are 12*7=84 REs on each RB. When the length of each time slot is 0.5 ms, two continuous time slots form one subframe, so the length of each subframe is 1 ms. Because one TB at least occupies one subframe in the time domain, one TB may need to occupy multiple OFDM symbols in the time domain. If a factor that a control channel (e.g. a Physical Downlink Control Channel (PDCCH)) also occupies a part of the OFDM symbols is taken into consideration, then the number of the OFDM symbols actually occupied by one TB may be less than 14, but usually greater than 10.
FIG. 5 is a schematic diagram of a method for physical channel mapping in an LTE system. As shown in FIG. 5, in an OFDM system, information transmission is usually performed by taking one TB as a unit. One TB may include one or more code blocks. Each code block may be subjected to encoding and rate matching processing before one encoded code block can be generated. Each encoded code block may be formed into one symbol stream after modulation. That is, one TB may correspond to multiple symbol streams, for example, J1, J2, . . . , Jn. In the LTE and LTE-A system, one TB may occupy a maximum of 4 layers, and may occupy the same time frequency resource area on each layer. A transport layer is a concept of multi-antenna “layer” in the LTE and LTE-A system, indicating the number of effective independent channels in spatial multiplexing. The concept “layer” is another dimension except time and frequency.
In the LTE and LTE-A system, 9 different transmission modes are defined for data transmission, and different transmission modes respectively correspond to single-antenna transmission, antenna diversity, beamforming and spatial multiplexing. In different transmission modes, a transmitting terminal may adopt different transmission strategies and parameters. A Down Control Information (DCI) format is a command word related to the transmission mode. The DCI may include: signaling related to downlink scheduling allocation and uplink scheduling request, physical channel resource allocation information, transmission formats (like a code rate, and a modulation order), spatial multiplexing (like a precoding matrix and the number of spatial layers), information related to Hybrid Automatic Repeat Request (HARQ) and information related to power control. The DCI may be transmitted in the PDCCH.
According to different functions, multiple types of Radio Network Temporary Identifiers (RNTIs) may be provided in the LTE system. Each User Equipment (UE) may correspond to multiple RNTIs at the same time. Functions like system broadcast and specific user scheduling may be implemented by using the RNTI to scramble a PDCCH control message.
Block encoding is an encoding technology between data packets, namely a process of generating a check data packet by encoding multiple source data packets. The block encoding is a process of generating a check sequence at a corresponding position of the check data packet based on an information sequence at the corresponding position of a source data packet. Each check data packet may include data at the corresponding position of each check sequence. There may be various methods for block encoding, for example, it may be feasible to generate the check data packet by performing an XOR operation to each source data packet, or by adopting a Reed-Solomon code, or by a Fountain code or network code. The block encoding may provide a better transmission performance by increasing an encoding constraint between the data packets.
Code block division is an essential process in a channel encoding chain processing flow. However, during an application process of the code block division, a time delay has not been fully considered. By taking a method for code block division in the 3GPP LTE system for example, the length of each code block after the code block division may be between 3000 bits to 6120 bits. When a bandwidth is relatively small, each code block may occupy multiple continuous OFDM symbols in the time domain, and the receiving terminal may decode a code block only after receiving all these OFDM symbols. If a system is sensitive to a time delay (e.g. Internet of Vehicles), decoding the data subjected to the code block division may cause a time delay that the system cannot accept. Therefore, for a system having a high requirement on the time delay, the code block division technology may influence normal operation of the system.